iOS App/Keyboard Plugin Invalidated

So I have been taking on the task to learn Swift and the XCode interface to get into iOS development. To do this, I have been practicing with a few projects that will help get me some exposure on all of this, so I took up one project that makes a custom keyboard. However, since I am guessing the tutorials are written in older versions of Swift/XCode, that I keep getting errors, one in particular.

Anytime I go into Settings and add my custom keyboard, I go to use it, and whenever I toggle it in the Keyboard Switcher, the keyboard crashes and defaults back to original iOS keyboard (This happens on both the Simulator and my phone. Also, the target iOS is correct). Upon that crash, I get this error: